Coupler height

Coupler height

Postby Rob M » Sat May 12, 2012 4:27 pm

I'm a little confused about proper coupler height and how much tolerance is acceptable. The Kadee #714 is 1/8" thick and the knuckle looks like it is centered height-wise. The NMRA standards say it should be .281” to the center of the knuckle. Elmer’s coupler height gauge puts it at .2685”

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Re: Coupler height

Postby ConducTTor » Sat May 12, 2012 5:28 pm

Hm. I'm a little confused as well.
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Re: Coupler height

Postby areibel » Sat May 12, 2012 7:46 pm

This is right up Chris Happe's alley, I'll send him an email and ask him for clarification.
I do see one possibility- on the NMRA's coupler page (http://www.nmra.org/standards/sandrp/pd ... 010.07.pdf)
it says the centerline is .281 but there's a tolerance of .013 plus or minus. And there's something in the remarks column about a "1/4 Rule: .0225", whatever that means!
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Re: Coupler height

Postby Rob M » Sat May 12, 2012 8:00 pm

Well crud, I didn't even see the tolerances listed there :doh: . I just found the size I was looking for and closed the window.

Mostly I'm curious what coupler height everyone uses so I can shoot for that. Then a variance of +/- .013 would be within specs. If I go by Elmer's guage and end up .01 low it would be out of nmra specs.
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Re: Coupler height

Postby areibel » Sat May 12, 2012 8:13 pm

I'll have to see if I can find my coupler gauge and see what it measures out at, but right now my basement looks like a tornado went through! The other thought i have is if they give that tolerance but you're using Micro Trains couplers how would that affect it? I have some rolling stock with 714's mounted, but I've pretty much switched over to 1025's for anything new. They do couple together fine, but maybe I've just been lucky!
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Re: Coupler height

Postby Rob M » Sat May 12, 2012 8:31 pm

The 1025's (left) are .095" high so they would be .015" higher to the center when under-mounted.

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Re: Coupler height

Postby areibel » Sat May 12, 2012 8:58 pm

I wonder if that's where the difference comes in? I'd have to ask Elmer to find out, but if he made two different height gauges, one for 714's and one for 1025's? or if there's one, from the drawing you posted if it's up .015 that would put it almost dead on (C/L) for 1025's, and the 714's would be within tolerance?
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Re: Coupler height

Postby Rob M » Sat May 12, 2012 9:27 pm

It says it's made for the 714's on his catalog page. No mention of one for the 1025's
http://www.ttscale.com/catalog/w-catalog.html
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Re: Coupler height

Postby railtwister » Sat May 12, 2012 10:55 pm

Hi Rob,

I'd say stick with NMRA lacking any other info. Also, its usually easier to add a thin shim if the couplers a bit too high than it is to raise a coupler whose mount is too low (I don't like putting washers on the trucks because that raises everything, not just the couplers!

The couplers I'm using are the MTL 1025 N scale couplers, on the premise that they are a bit too big for N scale, so they should look about right for TT. I forget what height I've been using, I'll have to check. For my other scales, I have made my own height gauge, it's pretty easy once you have the specs. However, it's not like I have too many cars to change if I see something I like better!

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Re: Coupler height

Postby Bill Dixon » Sun May 13, 2012 12:16 am

Almost all knuckle couplers are too large for their scale.

Kadee HO scale couplers are the correct size for S-Scale.
Kadee HOn3 couplers are the correct size for HO.
MicroTrains Z-Scale couplers are the correct size for N-Scale.

That makes the MicroTrains N-Scale couplers the right size for TT-Scale.

Most modelers do not worry about the over sized couplers as their larger size allows for more variation in track work.
Those who use the smaller correct size couplers on their layouts tend to be more careful in their track work as if they don't they have more unwanted uncouplings.

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